Francesca Mangione

Régénération partielle de la pulpe à partir de cellules mésenchymateuses dans un model préclinique porcin: La pulpe dentaire est un tissu connectif innervé et vascularisé, contenu dans une structure minéralisée inextensible formée par l’émail, la dentine et le cément. Ce tissu assure l’homéostasie et la sensibilité de la dent. Il est sujet à des lésions sévères faisant suite à une carie ou à un traumatisme. La thérapeutique conventionnelle préconisée alors est le traitement endodontique, qui consiste en l’exérèse de la totalité du tissu pulpaire et le comblement de l’espace évidé par un matériau synthétique bioinerte. Malgré les résultats cliniques satisfaisants, cette thérapeutique induit une fragilisation de la dent et une plus grande susceptibilité aux infections, qui peuvent conduire à terme à la perte de la dent. En se basant sur la présence de cellules souches mésenchymateuses dans la pulpe dentaire, des stratégies de régénération alternatives au traitement endodontique traditionnel sont à l’étude, afin de permettre le maintien des fonctions de nutrition et de sensibilité de la pulpe, garantes de la pérennité de la dent sur l’arcade. Elles s’inscrivent dans deux approches: la régénération de novo, en cas de nécrose du tissu pulpaire et la régénération partielle, lorsque seul le tissu pulpaire endommagé est éliminé et régénéré. Nos travaux portent sur la faisabilité de cette dernière approche dans un modèle préclinique. En effet, dans la perspective d’un transfert vers la clinique humaine, des modèles chez le gros animal doivent être développés afin de tester la faisabilité et le succès de cette thérapie, dans des conditions proches de la clinique. Du fait de ses similitudes avec l’homme en termes d’anatomie et de physiologie, le miniporc représente un modèle de choix pour les études précliniques d’ingénierie pulpaire. L’objectif principal de cette étude est de tester la faisabilité de la régénération pulpaire partielle, en implantant des cellules pulpaires porcines (pDPCs) contenues des hydrogels injectables dans des défauts pulpaires artificiellement créés chez le miniporc. Au cours ce travail, différentes techniques d’imagerie d’évaluation du processus de régénération ont été développées. En particulier, un protocole d’angiographie tridimensionnelle in- pour la visualisation du réseau vasculaire pulpaire a été mise au point. Par ailleurs, en utilisant des paramètres morphométriques spécifiques, initialement développés pour caractériser l’os, une analyse tridimentionnelle par micro-CT des tissus minéralisés de réparation a été élaborée. En appliquant un “split mouth model”, les hydrogels injectables ensemencés ou non par des pDPCs ont été implantés dans des molaires et des prémolaires, après amputation de la pulpe camérale. À 21 jours après la chirurgie, les analyses d’imagerie, d’histologie et d’immunologie ont mis en évidence, qu’indépendamment de la présence des pDPCs, l’implantation des hydrogels a induit la formation d’un pont d’ostéodentine. La caractérisation morphométrique tridimensionnelle a montré que la microarchitecture de ce pont différait largement de la dentine native. De plus, en présence des pDPCs, le processus de réparation était modifié, avec une moins bonne étanchéité du pont. Au cours de ce travail, une technique de suivi non invasive de la régénération a tenté d’être mise au point. Une angiographie tridimensionnelle par soustraction a été réalisée avant et après la procédure de régénération pulpaire partielle. Si les angiographies ont révélé l’entière vascularisation des mâchoires et des dents à croissance continue, l’apport vasculaire des dents matures traitées, du fait de son faible flux, n’a pas pu être mis en évidence. L’absence de régénération partielle de la pulpe dans les conditions testées souligne l’importance des modèles précliniques pour identifier les facteurs promouvant un environnement favorable à la régénération, dans la perspective d’un transfert vers la clinique humaine.

Orofacial bone tissue engineering addresses bone loss caused by trauma, malformations, or tumors, enabling restoration and implant rehabilitation. Angiogenesis plays a crucial role in osteogenesis by ensuring nutrient and oxygen transport essential for bone regeneration. Preclinical large animal models are vital for translational research and require noninvasive, nondestructive methods aligned with 3Rs principles (Replacement, Reduction, and Refinement) to assess angiogenesis. This study proposes high-resolution cone-beam computed tomography subtraction angiography (HR-CBCT-SA) adapted for the orofacial region as an innovative method for monitoring angiogenesis during jawbone regeneration. Three Yucatan minipigs with a surgically created buccal wall jawbone defect per hemimandible were followed for 90 days by CBCT-SA to assess vascular remodeling. Morphometric parameters, including vessel number, node count, radius, and length, were analyzed and validated against histological morphometry. CBCT-SA revealed vascular dynamics during healing. By day 10, increased vessel and node counts along with reduced vessel radius and length indicated neoangiogenesis. At day 30, vessel maturation was aligned with transition of fibrous tissue to osteoid matrix deposition. By day 90, vascular metrics stabilized, reflecting bone remodeling phases characterized by replacement of lamellar and medullary bone replacement. Extrabony vascular networks underwent more pronounced changes than intrabony vessels, underscoring the leading role of periosteum in regeneration. Histology validated CBCT-SA findings, although resolution limitations prevented detection of vessels smaller than 500 µm. Nevertheless, CBCT-SA captured angiogenic changes over time and supported nondestructive monitoring without compromising tissue integrity. This study establishes HR-CBCT-SA as a reliable, nondestructive imaging technique for assessing vascular changes during jawbone regeneration in preclinical models. It demonstrates significant translational potential because of the clinically validated use of CBCT-angiography. Advances in artificial intelligence (AI)-driven image analysis are expected to enhance sensitivity and accuracy, improving vascular assessment. Moreover, this approach can be extended for investigating vascular-related oral pathologies (e.g., radiochemical osteonecrosis of the jaws), offering valuable tool to advance research in jawbone regeneration.

The regenerative endodontic procedure (REP) represents a treatment option for immature necrotic teeth with a periapical lesion. Currently, this therapy has a wide field of pre-clinical and clinical applications, but no standardization exists regarding successful criteria. Thus, by analysis of animal and human studies, the aim of this systematic review was to highlight the main characteristics of the tissue generated by REP. A customized search of PubMed, EMBASE, Scopus, and Web of Science databases from January 2000 to January 2022 was conducted. Seventy-five human and forty-nine animal studies were selected. In humans, the evaluation criteria were clinical 2D and 3D radiographic examinations. Most of the studies identified a successful REP with an asymptomatic tooth, apical lesion healing, and increased root thickness and length. In animals, histological and radiological criteria were considered. Newly formed tissues in the canals were fibrous, cementum, or bone-like tissues along the dentine walls depending on the area of the root. REP assured tooth development and viability. However, further studies are needed to identify procedures to successfully reproduce the physiological structure and function of the dentin–pulp complex.

The recent advances in the field of cell-based therapeutics open promising perspectives for oral tissue regeneration. The development of large animal models, which overcome the limits of the rodent models and allow to emulate clinical situations, is crucial for the validation of regenerative strategies to move toward clinical application. Currently, porcine, canine, and ovine models are mainly developed for oral regeneration and their specific characteristics have an impact on the outcomes of the studies. Thus, this systematic review investigates the application of porcine, canine, and ovine models in present cell-based oral regeneration, according to the species characteristics and the targeted tissue to regenerate. A customized search of PubMed, EMBASE, Scopus, and Web of Science databases from January 2015 to March 2020 was conducted. Relevant articles about cell-based oral tissues engineering in porcine, canine, and ovine models were evaluated. Among the evaluated articles, 58 relevant studies about cell-based oral regeneration in porcine, canine, and ovine models matched the eligibility criteria and were selected for full analysis. Porcine models, the most similar species with humans, were mostly used for bone and periodontium regeneration; tooth regeneration was reported only in pig, except for one study in dog. Canine models were the most transversal models, successfully involved for all oral tissue regeneration and notably in implantology. However, differences with humans and ethical concerns affect the use of these models. Ovine models, alternative to porcine and canine ones, were mainly used for bone and, scarcely, periodontium regeneration. The anatomy and physiology of these animals restrain their involvement. If consistency was found in defect specificities and cell trends among different species animal models of bone, dentin-pulp complex, or tooth regeneration, variability appeared in periodontium. Regeneration assessment methods were more elaborate in porcines and canines than in ovines. Risk of bias was low for selection, attrition and reporting, but unclear for performance and detection. Overall, if none of the large animal models can be considered an ideal one, they are of deemed importance for oral cell-based tissue engineering and researchers should consider their relevance to establish favorable conditions for a given preclinical cell-based therapeutics. Impact statement: This systematic review investigates porcine, canine, and ovine models for current oral cell-based regeneration procedures, and researchers could refer to it for the choice of the most pertinent preclinical model for a given cell-based therapeutics.

Dose optimisation has been revisited in the literature due to the frequent use of cone beam computed tomography (CBCT). Although the reduction of the field-of-view (FOV) size has shown to be an effective strategy, this indirectly increases the negative effect from the exomass. The aim of this study was to evaluate the diagnostic accuracy of an optimised CBCT protocol in the detection of simulated vertical root fracture (VRF) in the presence of metal in the exomass and/or inside the FOV. Twenty teeth were endodontically instrumented and VRF was induced in half of them. All teeth were individually placed in a human mandible covered with a soft tissue equivalent material, metallic materials were placed at different dispositions in the exomass and/or endomass, and CBCT scans were obtained at two dose protocols: standard and optimised. Five radiologists evaluated the images and indicated the presence of VRF using a 5-point scale. Area under the ROC curve (AUC), sensitivity, and specificity were calculated and compared using ANOVA (α = 0.05). Overall, AUC, sensitivity, and specificity did not differ significantly (p > 0.05) between the dose protocols. In conclusion, optimised dose protocols should be considered in the detection of simulated VRF irrespective of the occurrence of artefacts from metallic materials in the exomass and/or inside the FOV.

Objectives: To evaluate the influence of exomass-related metal artefacts on the detection of simulated vertical root fracture (VRF) in cone-beam computed tomography (CBCT). Methods: Twenty teeth were endodontically instrumented and VRF was induced in half of them. All teeth were individually placed in an empty socket of a human mandible. Metallic materials were differently arranged in the exomass [zone outside of the field of view (FOV) but between the X-ray source and the receptor] and/or endomass (zone inside of the FOV), and CBCT scans were obtained. Four radiologists evaluated the presence of VRF using a 5-point scale. Sensitivity, specificity, and area under the receiver operating curve (AUC) were compared using ANOVA. Also, the tooth of interest was replaced with a tube filled with a radiopaque solution and all CBCT scans were repeated to analyse the data objectively. Mean grey and noise values were obtained from the tube and compared using ANOVA followed by Tukey’s test (α = 0.05). Results: Mean grey values were significantly lower and noise was significantly higher when metallic materials were present in the endomass or both the exomass and endomass. Sensitivity, specificity, and AUC were not influenced by the artefacts from the metallic materials irrespective of the arrangement condition. Conclusions: Exomass-related metal artefacts did not influence the diagnosis of simulated VRF in CBCT.